docs: clarify DO_NOT_TRACK values for GitHub CLI telemetry opt-out

DO_NOT_TRACK only disables telemetry when set to 1 or true, unlike GH_TELEMETRY which accepts any falsy value.

Author: BaconMan1168

content/github-cli/github-cli/github-cli-telemetry.md

@@ -105,7 +105,7 @@ You can opt out of the telemetry you see in the `log` mode described above using
 export GH_TELEMETRY=false
 ```
 
-Any falsy value works: `0`, `false`, `disabled`, or an empty string. You can also use the `DO_NOT_TRACK` convention:
+Any falsy value works: `0`, `false`, `disabled`, or an empty string. You can also use the `DO_NOT_TRACK` convention. Unlike `GH_TELEMETRY`, `DO_NOT_TRACK` only disables telemetry when set to `1` or `true`. Other values, such as `yes` or `enabled`, have no effect.
 
 ```shell
 export DO_NOT_TRACK=true